Preparation of c-alkyl hydroquinones and c-alkyl p-aminophenols



Patented Dec. 12, 1950 UNITED STiYIE-S PATENT OFFICE PREPARATIQN or o-Amg rp n nnooun NONES AND C-ALKYL p-AM-INOPHENOLS Frederic R. Bean, Rochester, "N; Yr, assigncr to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey No Drawing. Applicat'iii ifnily '16, 194s, Serial No. 395180 13 Claims.

solution of a mineral acid, e. g. sulfuric acid,

yields, not aniline nor phenylhydrox'ylamin'e, put rather p-ai'ni'no'phenol. I have now found that p-nitroalkylbenzenes when treated the same manner yield C alkylhydroquinones and C-alkyl- -aminophenols even thought'ne para position of the starting nitro compound is occupied by an alkyl group.

It is, accordingly, an object of 'my invention to provide a process for reducing p-nitroalkyl he'n- 'zenes. A further object is to provide a process for preparing C-a'lkylhydroquinones and 'C -alkyl- -p'-amino'phenols. Still further objects Will become apparent hereinafter.

In accordance with my invention, I reduce a nitrophenylcompouh'd containing in the position para to the 'nitro group a primary alkyi group eontaining from 1 to 4 carbon atoms, simultaneously with aluminium and an aqueous solution of an acid; The aluminium which I employ is preferably usedin finely divided form; for example, as flakes or a powder. The a ueous solution of the acid advantageously contains not more than 50 per cent by Weight of acid, and I have four'id that aqueous somiions containing not mere than frdm in er cent by Weight or acid are especially useful in practicing the processor my invention. The quantity of acid used,- as wen as the concennation, should be incident to maintain an acid rnediurn until the reductidnis substantially coinplete Especially advantageous results have been obtained when sulfuric acid Was used, although other mineral acids such as phosphoric acid or hydrochloric acid; can be used. organic acids have also been round to be useful in practicing the process of my invention; and those acids having e. dissolution constant in water at C. not

smaller than that {if oxalic acid (first hydrogen) have been found to be especially useful. Acids which react with any of the intermediate or final products formed in my process under the condiavoid'd; For example,

due to its reactivity 1 tions employed are to be formic acid is to he aye: with the amine dl'ivitl'iivcu formed. Typical orgaiuc acids include oxalic acid, an insane sulfenic iiid er from. 1 ii 4 e rt -i i ewms e. a

2 ine'than'es'ulfonic, ethanesulfonic, propane-l-"sulfi i'nic, propane-Museum, n=butane-1=sulfonic, iscbutane=1-su1foiiic, sulfc'acetic, ,fi-hydfox'yethanesulfonic, etc. acids, a sulfonic acid of the benfi'ene series (e. g. benten'esulfonic, p toluenesul'f o nie, b-tblileilesulfohic, m-benzeriedisuifenie, 1,3,5:beiiznetiisuueiiie, etc. acids) and a sulfon'ic acid cf the naphthalene series (e. g. naphthalenea-sulfonic acid, naphthalene fi-sulfonic acid, 1,5- n'a hthaleneuisulfonic, '2;6-naphtna1enedisu1fon= is, etc). i reduction of the nitrophei'iy'l compound "containing in the position para to the nitro group alkyl group containing from 1 to '4 caruoniatcms with the aluminium and aqueous solution of the acid is advantageously effected at temperatures varying 50 'c. to 100 o Althcugh the temperature" is apparently not critical, especially eriie'ac'ious results have been obtained at temperatures betw en C. and C. In the case of the higher melting aromatic nitro com ounds containing an alkyl group in the para position; a water miscible solvent, such as etnyI alcohol, or a water immiscible solvent, such as a hydrocarbon, can be added to the reaction mixture to promote dis ersion in the aqueous acid.

VVhei'i I reduce my nitrophenyl compounds, containing iii the position para to the intro group a primary alkyl group containing from 1 to 4 carbon atoms, in the presence or aluminum and an aqueous solution or an acid; a (J-alkylnydrcquinone whose alkyl group is correspondingly a primary alkyl group containing from 1 to 4 carbon atoms is always obtained in substantial proportion. A minor or very small proportion of the corresponding p-alkylaiiiline is usually obtained in addition to the C-alky1hydroquinone When the primary alkyl group in the position para to the nitro group of my nitrophenyl compounds contains from 2 to 4 carbon atoms, there are obtained varying amuuiits of a 'c-alk'yl-pamincphenol, the amounts depending upon the m nimum of reaeucn and the type of compound being reduced. That is to say, that upon reduction of p nitrotoluene in the presence of amminium and an aqueous solution of an acid, such as sulfuric acid, for example, no Z-hydrQXy-ptoluidine (i-amino o-cresol) can be detected. I have found further that when nitrophenyl cornpounds, containing in the position para to the nitro group an alkyl group which is not a primary allgyl group, are reduced in the presence of ailu and an aqueous solution of an acid, the reaction proceeds in a manner contrary to that set forth above.

p-toluidine melting at 44 was present.

Example I .-TOZuhydroquinone 17.5 g. of p-nitrotoluene, 37.5 cc. of sulfuric acid (sp. g. 1.84) and 500 cc. water were heated to about 95 C. and maintained at that temperature while 7.5 g. of aluminium flakes were slowly added to the mixture over a period of 1.5 to 2 hours. The reaction mixture turned orange to reddish in color and finally became light yellow as the aluminium was added. The reaction mixture was stirred for about one hour after the aluminium has been added. The small amount of excess aluminium was then filtered off and the filtrate was subjected to steam distillation. A small amount of p,p-dimethyldiphenylamine came over (M. P. 78 to 79 0.). No cresol could be detected. The reaction mixture was cooled and extracted with 500 cc. of diethyl ether. Upon evaporting the ether extract, 4.5 g. of toluhydroquinone were obtained. On recrystallization from benzene and then from petroleum ether, it melted at 125 C. When a portion of the product toluhydroquinone was mixed with an authentic sample of toluhydroquinone, n depression in melting point of the sample was observed. the mixture melting at 124 C. to 125 C. It acted as a photographic developer and on oxidation the product toluhydroquinone gave toluquinone melting at 69 C.

The reaction mixture remaining after the extraction with petroleum ether was made alkaline to brilliant yellow paper by the addition of sodium sulfite and sodium carbonate. The mixture was then filtered, and the filtrate extracted with diethyl ether while the precipitate was washed with alcohol. After evaporation of alcohol washings and ether extract, 0.65 g. of C. was obtained. When it was mixed with an aqueous solution of sodium hydroxide, and the mixture extracted with diethyl ether, no p-aminophenol could be detected when the alkalinity of the aoueous alkali layer was reduced until it was only faintly alkaline by the addition of sodium bisulfite.

Example II .--TOZuhydroquinone 35 g. of p-nitrotoluene, '75 cc. of sulfuric acid (sp. g. 1.84) and 1000 cc. of water were heated to about 95 C. and maintained at that temperafinally became light yellow as the aluminium was added. At this point a noticeable odor of cresol The reaction mixture was stirred- .for about one hour after the aluminium was added and the small amount of excess aluminium was filtered off. On subjecting the filtrate to ,steam distillation, 2.5 to 3 cc. of p-cresol came .over.

On further steam distillation a small amount of p.1 -dimethyldiphenylamine came over (M. P. 78 C. to 79 C.). The reaction mix,-

ture was allowed to cool down to room temperature and was extracted with diethyl ether. Upon evaporating the ether extract 1'? gm. of toluhydroquinone were obtained. When recrystallized first from benzene and then petroleum ether, it melted at 125 C. It acted as a photographic developer when added to an aqueous solution of sodium sulfite and sodium carbonate. The p-toluidine present in the aqueous acid solution after extraction was not recovered.

Example III .-Ethylhydroqainone A mixture of 15 g. of p-nitroethylbenzene, 35 cc. of sulfuric acid (sp. g. 1.84) and 300 cc. of water was heated to C. and maintained at that temperature while 5 g. of aluminium flakes were added with vigorous stirring over a period of 1.5 to 2 hours. The reaction mixture turned orange to reddish in color and finally became light yellow as the aluminium was added. The reaction mixture was then stirred for an addi-.- tional hour after all of the aluminium had been added, and the small amount of undissolved aluminium was filtered off. The filtrate was extracted with diethyl ether, and upon evaporation of the ether extract, 3.6 g. of ethylhydroquinone were obtained. When this product was subjected to steam distillation a very small amount of a sweet smelling oil, the odor of which resembled acetonhenone, came over. When the product ethylhydroquinone remaining in the disti ling flask was recrystalliz d from water and then from a mixture of benzene and petroleum ether, it gave a melting point of 114 to 115 (3. It also acted as a photo raphic developer. It was found to co tain 69.46 per cent carbon and '7 13 per cent hydrog n (calculat d for carbon 69.52 per cent and for h drogen 7.3 per cent). Its identity was fu ther e t blished by oxidation to a ouinone havin a melting po nt of 375 C., which is the recorded melting point of ethylouinone.

The reaction mixt re remaining after extraction ith the diethyl et er was made alkaline to brilliant ye ow paper by the addition of sodium sulfite and sodium ca bonate and filtered hot. The filter cake was thorough y washed with ethyl alcohol whi e the fi t ate Was extracted with ethyl acetate. The washings were combined with the extraction liouid and the mixture evaporated to dryness to give 6.9 g. of an oilv solid. When 50 cc. of a 15 per cent solution of sodium hydroxide to which a small amount of sodium hynosulfite had been added was added to the oily solid, part of it dissolved in the liquid while the remainder formed a second lio id layer lighter than the alkaline solution. When this top liquid layer was extracted with diethyl ether and the ether evaporated off, p-ethylaniline was obtained as an oil having the odor of aniline. When purified by steam distillation, it was obtained as a clear, practically colorless liquid. Its sulfate was prepared by dissolving the p-ethylaniline in dilute sulfuric acid. The sulfate was found to have a carbon content of 56.71 per cent, a hydrogen content of 6.87 per cent and a nitrogen content of per cent). Actylation '01 the p-ethylanilinewith acetic anhydride in dilute aqueous l'acetic acid gave p-ethylacetanilide melting ati9l Itwas found to -have a carbon content of 73.5 per cent, a hydrogen content of 8.2 per cent and a nitrogen content of 8.3 per cent (calculated for carbon 73.57 :per cent, for hydrogen 8.58 per cent and for nitrogen 8.03 per cent).

"To the lower aqueous layer "remaining after the ether extraction sodium bisulfite was added until it was only slightly alkaline to brilliant yellow paper. A precipitate of Z-ethyl-p-aminoph'enol having'the formula:

was obtained in the form of light-coloredcrystals. On drying 4 g. of crude product remained. It was recrystallized from benzene to give asolid melting at 168 to -168.5 C. with decomposition and discoloration. Typical of the behavior of aminophenols, it dissolved in cold aqueous sodiumv hydroxide, was insoluble in cold aqueous sodium carbonate, but was dissolved by cold dilute mineral acids. Its alkalinesolution darkened-rapidly due to aerial oxidation, and it was found to act as a photographic developer when dissolved in aqueous sodium carbonate-sodium sulfite solution. The 2-ethyl-p-aminophenol was proved to be a p-aminophenol by diazotizing a portion of the product obtained above with cold dilute sulfuric acid and sodium nitrite, and decomposing the diazo compound formed by boiling in a hot solution of about 10 per cent aqueous sulfuric acid. The dihydroxybenzene compound so obtained did not form a precipitate when treated with 21.20% lead acetate solution and had a melting point of 114 to 115 C. These data indicated the dihydroxybenzene compound was not derived from an o-aminophenol, and it gave the same melting point as ethylhydroqui-none. small quantity of the 2-ethyl-p-aminophenol was oxidized with dich-romic acid (sulfuric acid plus potassium dichromate), ethyl-p-quinone melting at 37.5" C. was obtained. An o-aminophenol would have been oxidized completely and no nuinone could have been isolated. The Z-ethylp-aminophenol gave a hydrochloride which was found to contain 54.89 per cent carbon, 6.63 per cent hydrogen and 8.30 per cent nitrogen (calculated for carbon 55.04 per cent, for hydrogen. 6.93 per cent and for nitrogen 8.02 per cent). Since the reduction of p-nitroethylbenzene could have given 3-ethyl-p-aminophenol instead of Z-ethylp-aminophenol, the-aminophenol of the above example (designated Sample A in the table below) was compared with 3-ethyl-p-aminophenol:

(designated Sample B in the table below) prepared from 3-ethylphenol by nitrosation and reduction of the nitroso derivative to the amino phenol and another specimen of 3-ethyl-p-aminophenol prepared from o-nitroethylbenzene (designated Sample C in the table below) by re- When a 6 duction "with aluminium and aqueous sulfuric acid (Bean application Serial 'No. 547,296, filed July 29, 1944). The results are given in the table below:

1 Calculated; 040.02%; H-8.08%; N-l0.21%.

3 Analysis for hydrochloride given above.

From the above table it can be seen that the aminophenol resulting from the reduction of pnitroethylbenzene contains its ethyl group in the 2-position, since only two isomers are possible, and the derivatives of Samples B and C (both 3-ethyl compounds) show that this aminophenol (Sample A) is not a 3-ethyl compound.

Example I V.77.-Pro'pylhydroquinone Jodor resembling that of a quinone.

I OH

8.25 g. of .p-nitro-propylbenzen'e, 15 cc. of

sulfuric acid (sp. g. 1.84) and 200 cc. of water were heated at 95 C. and maintained at that temperature while 3 g. of aluminium flakes were added over a period of 1.5 to 2 hours with vigiorous stirring.

The reaction mixture turned orange to reddish in color and finally became and the small amount of excess aluminium was :filtered on. The filtrate was cooled and then extracted with diethyl ether. After evaporation of the other from the extract, there remained 1.5 g.

of n-propylhydroquinone. It was recrystallized from a mixture of benzene and petroleum ether to give a pure product melting at 89 to 90 C. On oxidation with dilute aqueous potassium dichromate, it gave a yellow oil having a pungent The n-propylhydroquinone was soluble in ether and its aqueous solution with sodium sulfite and sodium lcarbonate acted as developers for exposed photographic paper and film. It had a carbon content of 71.7 per cent and a hydrogen content of 7.8 per cent (calculated for carbon 71.00 per cent and for hydrogen 7.88 "per cent). The reaction mixture which remained after extraction with the diethyl ether was made alkaline with sodium sulfite and sodium carbonate'and then filtered. The filter cake was washed with alcohol and the filtrate was extracted with diethyl ether. The washings were combined with the extract, and the mixture was made acid and evaporated to dryness. The dried residue was taken up in 50 cc. of water and an excess of 40% sodium hydroxide to which some sodium sulfite and sodium hyposulfite had been added was stirred into the aqueous solution. An oily layer' formed on "top the aqueous lower layer and-this .wasremoved in a separatory funnel. This oil, p-n-propylani line, was insoluble in sodium hydroxide, had a strong odor resembling that of aniline, and it acted as a photographic developer in sodium sulfite-sodium carbonate solutions. It was cnverted to its hydrochloride for analysis. The hydrochloride contained 62.8 per cent carbon, 8.1% hydrogen and 8.4 per cent nitrogen (calculated for carbon 62.89, for hydrogen 8.22 per cent and for nitrogen 8.10 per cent). The alkalinity of the lower aqueous alkaline layer remaining after removal of the oily layer was reduced by the addition of sodium bisulfite until it was only slightly alkaline to brilliant yellow paper. A precipitate of 2-n-propyl-p-aminophenol separated which was recrystallized from a mixture of benzene and petroleum ether to give a product melting at 91 C. and having the formula:

It was soluble in sodium hydroxide and also dilute acids. Its aqueous solutions with sodium sulfite and sodium carbonate acted as strong developers for exposed photographic paper or film. On oxidation with dichromic acid (sulfuric acid plus potassium dichromate), it gave npropyl-p-quinone as a yellow oil which was liquid at room temperature. On reduction, the npropyl-p-quinone gave n-propyl-p-hydroquinone having a melting point of 89 to 90 C. The 2-npropyl-p-arninophenol had a carbon content of 71.52 per cent, a hydrogen content of 8.64 per cent and a nitrogen content of 9.38 per cent (calculated for carbon 71.47 per cent, for hydrogen 8.60 per cent and for nitrogen 9.26 per cent). The propyl group in the aminophenol prepared by the reduction of p-nitro-n-propyl-benzene was proved to be in the 2-position by preparing 3-n-propyl-p-aminophenol and comparing the properties of the two compounds. The 3-npropyl-p-aminophenol was prepared by the reduction of o-nitro-n-propylbenzene according to the process described in Bean application 547,298, filed July 29, 1944, and after purification by recrystallization from a mixture of benzene and petroleum ether, it gave a pure product melting at 119 to 120 C. It analyzed 71.10 per cent carbon, 8.40 per cent hydrogen and 9.30 per cent nitrogen (calculated for carbon 71.47 per cent, for hydrogen 8.60 per cent and for nitrogen 9.26 per cent). Since the 3-n-propyl-p-aminophenol had a melting point far removed from that of the aminophenol obtained by the reduction of pnitro-n-propylbenzene and there are only two possible isomers for a n-propyl-p-aminophenol, the aminophenol obtained by the reduction of 'p-nitro-n-propylbenzene had a n-propyl group in the 2-position.

Example V.-n-Butylhydroquinone 8.95 g. of p-nitro-n-butylbenzene, cc. of suljfuric acid (sp. g.-1.84) and 250 cc oi water were heated to C. and maintained at that temperature while 2 g. of aluminium flakes were added over a period of 3 to 4 hours with vigorous stirring. The reaction mixture turned from yel low to red in color and finally changed to brownish yellow as the last of the aluminium was added. Since the reaction proceeded quite slowly toward the end of the four-hour period of heating, the reaction mixture was stirred at 95 C. for an additional 1.5 hours after all of the aluminium had been added. The reaction mixture was then diluted to 750 cc. with water, and a small amount of gummy material and undissolved aluminium were filtered off while the mixture was still hot. After allowing the filtrate to cool, it was extracted with diethyl ether.' The ether was evaporated off from the extract to give 1.3 g. of nbutylhydroquinone. After recrystallization from a mixture of benzene and petroleum ether, the n-butylhydroquinone melted at 865 to 87 C. On analysis, it was found to contain 72.08 per cent carbon and 8.53 per cent hydrogen (calculated for carbon 72.24 per cent and for hydrogen 8.49 per cent). On oxidation with potassium dichromate in dilute aqueous sulfuric acid, it gave n-butyl-p-quinone as a light yellow product having a noticeable quinone odor and a melting point of 315 C. The n-butylhydroquinone was soluble in aqueous caustic alkalis and diethyl ether, but was insoluble in dilute mineral acids. It acted as a photographic developer and could be employed as an antioxidant for gasoline, oils, rubber, etc. I

The reaction mixture remaining after the extraction with diethyl ether was cooled to 0 C. and 3.85 g. of precipitate separated out. On evaporating the mixture to 250 cc. and cooling to 0 C. again, another 0.47 g. of precipitate was obtained. The mother liquor was made alkaline to brilliant yellow paper by the addition of sodium sulfite and sodium carbonate and filtered hot. The filter cake was washed with hot ethyl alcohol and the filtrate was extracted with diethyl ether. The washings were combined with the ether extract and the mixture made acid to Congo red with dilute sulfuric acid, and then evaporated to dryness. The 2.5 g. of dried product so obtained were combined with the 3.85 g. and 0.47 g. of precipitate obtained above by cooling the reaction mixture. The mixture of solids was mixed with water and made strongly alkaline with excess sodium hydroxide. An oily layer formed on top of the alkaline aqueous layer and was extracted with diethyl ether. The ether was evaporated from the extract to give 2.7 g. of p-nbutylaniline having a strong aromatic amine odor. It was converted to the sulfate which gave a melting point of 210 to 215 C. with discoloration. The sulfate on analysis was found to contain 60.6% per cent carbon, 8.18 per cent hydrogen and 7.06 per cent nitrogen (calculated for carbon 60.6 per cent, for hydrogen 8.1 per cent and for nitrogen 7.02 per cent). The sulfate was soluble in alkali and dilute aqueous acids. The alkalinity of'the lower aqueous alkaline layer remaining after extraction with diethyl ether was reduced by the addition of sodium bisulfite and a small amount of dilute hydrochloric acid until it was only slightly alkaline to brilliant yellow paper. A precipitate separated out at once, and the aqueous layer was cooled and then filtered. There were thus obtained 1.26 g.' of n-butyl-p-aminophenol. After recrystallization from a mixture of benzene and petroleum ether, it melted at 81 to 82 C. On analysis it contained73.06 per cent carbon, 8.84- per cent hydrogen and 8.63 per cent nitrogen (calculated for carbon 72.67 per cent, for hydrogen 9.15 per cent and for nitrogen 8.47 per cent). It was soluble in aqueous caustic alkali and dilute aqueous acids, and it also acted as a photographic developer. On oxidation with dichromic acid (potassium dichromate plus sulfuric acid) it gave n-butyl-p-quinone as a yellow solid (an o-aminophenol would have been completely oxidized). on reduction of the quinone with aqueous sodium hyposulfite'it gave n-butylhydroquinone as a solid melting at 86 to 87 C. To prove that the n-butyl group in the p-aminophenol obtained by the reduction of p-nitro-n-butylbene zene was in the 2-position, its properties were compared with those of 3-n-butyl-p-aminophee nol prepared by the reduction of o-nitro-n-butyl-benzene prepared according to the process described in Bean application SerialNo. 547,296. The 3-n-butyl-p-aminophenol so prepared had the formula:

NLHT

and after recrystallization from a mixture of benzene and petroleum ether it melted at 80 to 81 C. On microanalysis, it contained 72.6 per cent carbon, 9.0 per cent hydrogen and 8.2 per cent nitrogen (calculated for carbon 72.67 per cent, for hydrogen 9.15 per cent and for nitrogen 8.47 per cent). It was soluble in aqueous sodium hydroxide and dilute aqueous acids, On oxidation with dichromic acid (potassium dichromate plus aqueous sulfuric acid) the 3-nbutyl-p-aminophenol gave n-butyl-p-quinone melting at 31.5 G. Since the melting point of the n-butyl-p-aminophenol prepared by the reduction of p-nitro-n-butylbenzene was too close to the melting point of the 3-n-butyl-p-aminophenol to serve as a means of differentiation, 9. mixed melting point determination was made. A mixed melting point of 60 C. to.70 C. was obtained which showed that the two compounds were not identical. Since there are only two possible n-butyl-p-aminophenols and the n-butylp-aminophenol obtained by thereduction of p.- nitro-n-butylbenzene was not identical to the 3"-' n-butyl-p-aminophenol obtained by the reduction of o-nitro-n-butylbenzene, the former compound must contain its-n-butyl group in the 2- position, thus:

NHg.

Instead of adding the aluminium flakes .to the the mixture of the p-nitroalkylbenzene;:: water and sulfuric acid as is" donein the abcve'exam ples, a. sulfuric acid solution. in water canv be added to a hot, stirred suspensiomoi aluminium in. water and. the. nitroalkylbenzene. Other. acids can be advantageously employed5in=placezof the sulfuric acid in the above examples, such as oxalic.

acid, phosphoric acid, hydrochloric acid, the alkane-sulfonic acids (e. g. methanesulfonic acid, ethanesulfonic acid, etc.) and the aromatic sul-' fonic acids (e. g. those of the benzene and naphthalene series, such as p-toluenesulfonic acid, c-naphthalene-sulfonic acid, etc.)-.

Example VI A mixture of 15 g. of p-nitroethylbenzene, 40 g. of. oxalic acid and 200 g. of water was heated at -l00 C., and maintained at that temperature while 5 g. of aluminum flakes were added with vigorous stirring over a period of 1 /2 to 2 hours. The reaction mixture was stirred an additional 1 /2 to 2 hours after all of the aluminum had been added. The undissolved aluminum was filtered offv and. the reaction mixture was subjected to steam distillation. A very small amount of sweet smelling oil came over. Its odor resembled acetophenone.

The cooled reaction mixture was extractedv with diethyl ether. Upon evaporation of the ether about 4. g. of ethyl hydroquinone were obtained.

The reaction mixture, after ether extraction, was made hot and then made alkaline to brilliant yellow paper with sodium sulfite and sodium carbonate. Some p-aminoethylbenzene came out'of solution at this point and was separated off. On cooling. the alkaline solution, 2-ethyl-p-aminophenol; precipitated with some p-aminoethylbenzene. These organic bases were filtered ofiand then treated with a small amount of sodium hyposulfite and an excessv of sodium hydroxide solution causing the Z-ethyl-p-aminophenol to dissolve and the p-aminoethylbenzene to separate as an oil. The oil was extracted with a small amount. of ether. On evaporation it was converted to the hydrochloride with hydrochloric acid and 2 g. of product were obtained.

The Z-ethyl-p-aminophenol contained in solution wtih the sodium hydroxide was precipitated by adding. sodium *bisulfit'e. 3 g. of product were obtained.

Operating in a similar manner, other acids and nitrobenzenes containing a primary alkyl group in the paraposition can advantageously be utilized in'the' process of my invention.

What I claim and desire secured by Letters Patent of. the United States is:

l. A process for preparing an alkyl substituted hydroquinone comprising reducing a nitrophenyl compound containing in thepara position a primary alkyl group having from 1- to 4 carbon atoms, simultaneously with finely divided aluminium and an aqueous solution of an acid selected from the groupconsisting of sulfuric acid, phosphoric acid, hydrochloric acid, oxalic acid, an alkane sulfonic acid: containing from 1 to 4 carbon atoms, a sulfonic acid of the benzene series and a sulfonic acid of the naphthalene series, said solution containing not more than 50% by weight of said acid, the quantity of said acid present being suficient to maintain an acid me dium until the reduction is substantially com plete, and separating the alkyl-substituted hydro quinone from the reaction mixture.

2. A process for preparing an alkyl substituted hydroquinone comprising reducing a nitrophenyl compound containing in the: para position a primary alkyl group having from 1 to 4 carbon atoms simultaneously with finely divided aluminium and an aqueous solution of sulfuric acid, said solution containing not more than 50% by Weight of said acid,'lthe2quantity of said acid present being sufficienttto maintain amacid medium until: the w ii duction is substantially complete, and separating the alkyl-substituted liydroquinone from the reaction mixture.

3. A process for preparing an alkyl substituted hydroquinone com-prising reducing a nitrophenyl compound containing in the para position a primary alkyl group having from 1 to 4 carbon atoms, simultaneously with finely divided aluminium and an aqueous solution of an acid selected from the group consisting of sulfuric acid, phosphoric acid, hydrochloric acid, oxalic acid, an alkane sulfonic acid containing from 1 to 4 carbon atoms, a sulfonic acid of the benzene series and a sulfonic acid of the naphthalene series, said solution containing not more than by weight of said acid, the quantity of said acid present being sufficient to maintain an acid medium until the reduction is substantially complete, and separating the alkyl-substituted hydroquinone from the reaction mixture. 4. A process for preparing an alkyl substituted hydroquinone comprising reducing a nitrophenyl compound containing in the para position a primary alkyl group having from 1 to 4 carbon atoms simultaneously with finely divided aluminium and an aqueous solution of sulfuric acid, said solution containing not more than 10% by weight of said acid, the quantity of said acid present being sufiicient to maintain an acid medium until the reduction is substantially complete, and separating the alkyl-substituted hydroquinone from the reaction mixture.

5. A process for preparing an alkyl substituted hydroquinone comprising reducing, at a temperature of from 50 C. to 100 C., a nitrophenyl compound containing in the para position a primary alkyl group having from 1 to 4 carbons atoms. simultaneously with finely divided aluminium and an aqueous solution of an acid selected from the group consisting of sulfuric acid, phosphoric acid, hydrochloric acid, oxalic acid, an alkane sulfonic acid containing from 1 to 4 carbon atoms, a sulfonic acid of the benzene series and a sulfonic acid of the naphthalene series, said solution containing not more than 50% by weight of said acid the quantity of said acid present being suincient to maintain an acid medium until the reduction is substantially complete, and separating the alkyl-substituted hydroquinone from the reaction mixture.

6. A process for preparing a mixture of an alkyl hydroquinone selected from those represented by the general formula:

whereinR represents a primary alkyl group having from 2 to 4 carbon atoms, and an alkyl p-aminophenol selected from those represented by the general formula:

wherein R represents a primary alkyl group having from 2 to 4 carbon atoms, comprising reducing a compound'selected from those represented by the general formula:

IIIOQ wherein R represents a primary alkyl group having from 2 to 4 carbon atoms, with finely divided aluminium and an aqueous solution of an acid selected from the group Consisting of sulfuric acid, phosphoric acid, hydrochloric acid, oxalic acid, an alkane sulfonic acid containing from 1 to 4 carbon atoms, a sulfonic acid of the benzene series and a'sulfonic acid of the naphthalene series, said solution containing not more than 50% by Weight of said acid, the quantity of said acid present being sufiicient to maintain an acid medium until the reduction is substantially complete.

7. A process for preparing a mixture of an alkyl hydroquinone selected from those represented by the general formula:

wherein R represents a primary alkyl group having from 2 to 4 carbon atoms, and an alkyl p-aminophenol selected from those represented by the general formula:

NHz

wherein R represents a primary alkyl group having from 2 to 4 carbon atoms, comprising reducing, at a temperature of from 50 C. to C., a compound selected from those represented by the general formula:

wherein R represents a primary alkyl group having from 2 to 4 carbon atoms, with finely divided aluminium and an aqueous solution of an acid selected from the group consisting of sulfuric acid, phosphoric acid, hydrochloric acid, oxalic acid, an alkane sulfonic acid containing from 1 to 4 carbon atoms, a sulfonic acid of the benzene series and a sulfonic acid of the naphthalene series, said solution containing not more than 50% by weight of said acid, the quantity of said acid present being suflicient to maintain an acid medium until the reduction is substantially complete. a

13' 3. A process for preparing a mixture of an alkyl hydroquinone selected from those represented by the general formula:

wherein R represents a primary alkyl group having from 2 to 4 carbon atoms, and an alkyl p-aminophenol selected from those represented by the general formula:

I NH2 wherein R represents a primary alkyl group having from 2 to 4 carbon atoms, comprising reducing, at a temperature of from 50 C. to 100 C., a compound selected from those represented by the general formula:

wherein R represents a primary alkyl group having from 2 to 4 carbon atoms, with finely divided aluminium and an aqueous solution of an acid selected from the group consisting of sulfuric acid, phosphoric acid, hydrochloric acid, oxalic acid, an alkane sulfonic acid containing from 1 to 4 carbon atoms, a sulfonic acid of the benzene series and a sulfonic acid of the naphthalene series, said solution containing not more than by weight of said acid, the quantity of said acid present being sunicient to maintain an acid medium until the reduction is substantially complete.

9. A process for preparing a mixture of an alkyl hydroquinone selected from those represented by the general formula:

wherein R represents a primary alkyl group having from 2 to 4 carbon atoms, and an alkyl p-aminophenol selected from those represented by the general formula:

wherein R represents a primary alkyl group having from 2 to 4 carbon atoms, comprising reduc- 141 ing a compound selected from those represented by the general formula:

wherein R represents a primary alkyl group having from 2 to 4 carbon atoms, with finely divided aluminium and an aqueous solution of sulfuric acid, said solution containing not more than 50% by weight of said acid, the quantity of said acid present being sufficient to maintain an acid medium until the reduction is substantially complete H 10. A process for preparing a mixture of an alkyl hydroquinone selected from those represented by the general formula:

wherein R represents a primary alkyl group having from 2 to 4 carbon atoms, and an alkyl p-aminophenol selected from those represented by the general formula:

wherein R represents a primary alkyl group having from 2 to 4 carbon atoms, comprising reducing, at a temperature of from 50 C. to 100 C., a compound selected from those represented by the general formula:

wherein R represents a primary alkyl group having from 2 to 4 carbon atoms, with finely divided aluminium and an aqueous solution of sulfuric acid, said solution containing not more than 10% by weight of said acid, the quantity of said acid present being sufiicient to maintain an acid medium until the reduction is substantially complete.

11. A process for preparing a mixture of ethylhydroquinone and 2-ethyl-p-aminophenol comprising reducing, at a temperature of from C. to C., p-ethylnitrobenzene simultaneously with finely divided aluminium and an aqueous solution of sulfuric acid, said solution containing not more than 10% by weight of said acid, the quantity of said acid present being sufiicient to maintain an acid medium until the reduction is substantially complete.

12. A process for preparing a mixture of n-propylhydroquinone and 2-n-propyl-p-aminophenol 15 comprising reducing, at a temperature of from 80 C. to 100 0., p-nitropropylbenzene simultaneously with finely divided aluminium and an aqueous solution of sulfuric acid, said solution containing not more than 10% by Weight of said acid, the quantity of said acid present being sufficient to maintain an acid medium until the reduction is substantially complete.

13. A process for preparing a mixture of n-butylhydroquinone and Z-n-butyl-p-aminophenol comprising reducing, at a temperature of from 80 C. to 100 C., n-butylnitrobenzene simultaneously with finely divided aluminium and an aqueous solution of sulfuric acid, said solution containing not more than 10% by weight of said acid, the quantity of said acid present being sufiicient to maintain an acid medium until the reduction is substantially complete.

FREDERIC R. BEAN.

16 REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,492,094 Bielouss Apr. 29, 1924 2,132,454 Bassford Oct. 11, 1938 2,198,249 Henke Apr. 23, 1940 2,273,101 Haberland Feb. 1'7, 1942 FOREIGN PATENTS Number Country Date 4,389 Great Britain 1881 96,853 Germany Mar. 15, 1898 OTHER REFERENCES Degering: Organic Nitrogen Compounds (Univ. Lithoprinters, Ypsilanti, Mich., 1945), page 134, para. 418. 

1. A PROCESS FOR PREPARING AN ALKYL SUBSTITUTED HYDROQUINONE COMPRISING REDUCING A NITROPHEYL COMPOUND CONTAINING IN THE PARA POSITION A PRIMARY ALKYL GROUP HAVING FROM 1 TO 4 CARBON ATOMS, SIMULTANEOUSLY WITH FINELY DIVIDED ALUMINUM AND AN AQUEOUS SOLUTION OF AN ACID SELECTED FROM THE GROUP CONSISTING OF SULFURIC ACID, PHOSPHORIC ACID, HYDROCHLORIC ACID, OXALIC ACID, AN ALKANE SULFONIC ACID CONTAINING FROM 1 TO 4 CARBON ATOMS, A SULFONIC ACID OF THE BENZENE SERIES AND A SULFONIC ACID OF THE NAPHTHALENE SERIES, SAID SOLUTION CONTAINING NOT MORE THAN 50% BY WEIGHT OF SAID ACID, THE QUANTITY OF SAID ACID PRESENT BEING SUFFICIENT TO MAINTAIN AN ACID MEDIUM UNTIL THE REDUCTION IS SUBSTANTIALLY COMPLETE, AND SEPARATING THE ALKYL-SUBSTITUTED HYDROQUINONE FROM THE REACTION MIXTURE.
 8. A PROCESS FOR PREPARING A MIXTURE OF AN ALKYL HYDROQUINONE SELECTED FROM THOSE REPRESENTED BY THE GENERAL FORMULA: 